Rough Idle – Engine Dies at Stops

My Subaru has a pulsing idle problem that I need your help with. When I crank up the engine when it’s cold, it idles around 500-550 RPMS (which is what it should be normally) but then once the engine is at normal warm operating temperature, the idle will start to pulsate. The idle speed will fluctuate up and down when I am sitting at idle, but only when the engine is warmed up.

Then the engine dies if I am idling at a stop light for awhile. If I turn on my A/C, it almost keep the car alive. Only when the A/C is increasing the idle does the pulsing go away and no stall occurs. When the A/C is turned off the pulsing come back.

On the low end of the pulse the dash lights dim.

I have checked the alternator and the test was positive. Reading around 14.3. I also had replaced the fuel injectors. Cleaned the o2 sensors and IAC valve. Checked the grounds. The wires plugs and coil pack are fairly new 10,000 miles. I have also cleaned the throttle body opening and my cars MAP sensor.

Can you please help me

Hey there,

I would still suspect a dirty throttle body, idle control motor or the base idle speed is set to low. I am not too familiar with your vehicle but I would suspect there is a cleanable idle control motor. I would also make sure there are no vacuum leaks under the hood with any of the rubber vacuum hoses and their connections.

Here is a video of proper throttle body cleaning


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